Darek Jon Nelson is charged with four felony counts in the death of 18-year-old Vinessa Lazano Friday night outside the Pizza Ranch restaurant in Montevideo, where both the defendant and the victim worked.

Authorities say Lozano, the single mother of a young son,died after being stabbed an estimated 30 times with a hunting knife.

A criminal complaint filed Monday in Chippewa County Court details how Nelson, a self-described loner who spent most of his time in his bedroom on the internet, haddeveloped an interest in Lozano.Nelson allegedly admitted to authorities that the relationship was "one-sided."

Investigators say Nelson called Lozano on the phone in early January and asked her to stop by the home owned by his parents. In an interview with detectives the defendant said that Lozano promised to visit, but never did.He allegedly became angry whenshe did not show up, andtold investigators she hadlied to him andthat he was sick of it.

The complaint says Nelson told police he soon began thinking of killing Lozano, and made a plan to bring his hunting knife to work that Friday.Nelson reportedly told officers thatLozano shunned him that evening and he decided to go through with his plan.

After both punched out around 8:45 p.m.,investigators say Nelson admits he followed the teen into the parking lot,ran up behind her and started stabbing her with the hunting knife. The criminal complaint indicates that Nelson kept stabbing Lozano, even after she had collapsed.

He is also charged with using the murder weapon to threaten a co-worker who tried to intervene and save Lozano.

Prosecutors say squad car video from the vehicle of the first arriving officer shows Nelson standing above the body of the victim with a knife in his hand.They say the tape then shows thedefendant crouching down and stabbing Lozano one more timebefore the officer orders him to drop the knife.

Darek Nelson is charged with second degree murder, first degree manslaughter, and two counts of assault. If found guilty he faces at least 40 years in prison.